The Global Positioning System (GPS) is based on the fixed location base stations and the measurement of time-of-flight of accurately synchronized station signature transmissions. The base stations for the GPS are geo-stationary satellites and require atomic clocks for synchronization.
GPS has several draw backs including relatively weak signals that do not penetrate heavy ground cover and/or man made structures. Furthermore, the weak signals require a sensitive receiver. GPS also utilizes a single or narrow band of frequencies that are relatively easy to block or otherwise jam. The accuracy of the GPS system relies heavily on the use of atomic clocks, which are expensive to make and operate.
In addition, GPS utilizes a relatively slow update rate; on the order of once per second, which makes it ill suited for use in autonomous navigation of a vehicle. For example, a vehicle traveling at 10 kph would move about 2.75 m in a second. For an autonomous vehicle, significant changes in terrain may occur in this distance, making an update rate of once per second much too slow.
Known triangulation methods are also numerical in nature, meaning that no direct solution is available to find the location of the target. Rather, these open-form solutions provide only a initial guess and iterative numerical solution to estimate the location of the target. The resolution and accuracy of the location determination suffers accordingly. Further, using an open form solution in three dimensions is very difficult. There has not previously been a method to directly calculate the location of the target. Such a direct calculation would necessary increase the resolution and accuracy of the location determination.
The present invention overcomes one or more of these problems.